One of the most significant recent developments in the technology of analytical techniques for biological mixtures is the technique of capillary electrophoresis. Capillaries provide distinct advantages in the separations of such species as small peptides, proteins and nucleic acids, since they can be used to analyze extremely small samples with convenient on-line spectroscopic detection, and they permit the use of high voltages, thereby achieving separations at relatively high speed.
The use of a gel as the separation medium in the capillary combines the advantages of capillary electrophoresis with the known capabilities of gel electrophoresis. Due to their unique geometry, however, capillaries present a distinct challenge, particularly in the preparation of the gel in the capillary. One troublesome factor is the difficulty of obtaining uniform gel consistency and concentration throughout the capillary. These are important in achieving component resolution and reproducibility, and are therefore important considerations in achieving optimal use of the technique, particularly with capillaries of very narrow bore. This is difficult to achieve with gels in capillaries, since the shrinkage of the gel, which is an inherent result of the polymerization reaction, causes gaps in the gel, particularly bubble-like open spaces, generally of microscopic dimensions, which create deviations from gel uniformity. Such discontinuities lead to current drop and disruption of the applied electric field gradient during electrophoresis, which in turn lower the efficiency, reliability and reproducibility of the separation.
Although techniques have been proposed to overcome this problem, they tend to require materials, equipment or procedures, which are not generally used in connection with capillaries, gel preparation or electrophoresis, and give varying results. The present invention addresses this need, in a simple, efficient, reproducible and reliable manner.